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<title>Issue 3376: "integer-like class type" is too restrictive</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#Resolved">Resolved</a> status.</em></p>
<h3 id="3376"><a href="lwg-defects.html#3376">3376</a>. "integer-like class type" is too restrictive</h3>
<p><b>Section:</b> 24.3.4.4 <a href="https://wg21.link/iterator.concept.winc">[iterator.concept.winc]</a> <b>Status:</b> <a href="lwg-active.html#Resolved">Resolved</a>
 <b>Submitter:</b> Jonathan Wakely <b>Opened:</b> 2020-01-16 <b>Last modified:</b> 2021-10-23</p>
<p><b>Priority: </b>3
</p>
<p><b>View all other</b> <a href="lwg-index.html#iterator.concept.winc">issues</a> in [iterator.concept.winc].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Resolved">Resolved</a> status.</p>
<p><b>Discussion:</b></p>
<p>
24.3.4.4 <a href="https://wg21.link/iterator.concept.winc">[iterator.concept.winc]</a> says:
</p>
<blockquote><p>
A type <code>I</code> is an <i>integer-class type</i> if it is in a set of implementation-defined class types 
that behave as integer types do, as defined in below.
</p></blockquote>
<p>
and
</p>
<blockquote><p>
A type <code>I</code> is integer-like if it models <code>integral&lt;I&gt;</code> or if it is an integer-class type.
</p></blockquote>
<p>
Some implementations support built-in integer types that do not necessarily model <code>std::integral</code>, 
e.g. with libstdc++ whether <code>std::is_integral_v&lt;__int128&gt;</code> is <code>true</code> depends whether 
"strict" or "extensions" mode is in use. Because <code>__int128</code> is not a class type, it can't be used 
as an integer-like type in strict mode (which effectively means it can't be used at all, to avoid unwanted 
ABI differences between modes).
<p/>
The requirement should be relaxed to permit non-class types which are integer-like but not one of the 
standard integer types (nor extended integer types). If we do that, the name "integer-like class type" 
should probably change.
</p>

<p><i>[2020-02-08 Issue Prioritization]</i></p>

<p>Priority to 3 after reflector discussion.</p>
<p><i>[2021-10-23 Resolved by the adoption of <a href="https://wg21.link/P2393R1" title=" Cleaning up integer-class types">P2393R1</a> at the October 2021 plenary. Status changed: New &rarr; Resolved.]</i></p>



<p id="res-3376"><b>Proposed resolution:</b></p>





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